Involvement with the criminal justice system, substance use, and infection with HIV and hepatitis C virus (HCV) are syndemic in the United States. Persons involved with the criminal justice (CJ) system are more likely to use substances, have comorbid mental health conditions, limited access to health care and health insurance, and have higher rates of HIV and HCV infection than the general population. Furthermore, incarcerated populations are also more likely to be racial and ethnic minorities and be economically and educationally disadvantaged. Research exploring these phenomena is insufficient. To address these disparities and increase the number and capacity of clinical scientists working with CJ populations, we established The Lifespan/Brown Criminal Justice Research Program on Substance Use and HIV (referred to as the CJRT) in 2014. Following a successful initial funding cycle during which we enrolled 22 scholars, we seek renewal funding to sustain this important and innovative training program. The CJRT program recruits an annual cohort of 4-5 scholars consisting of exceptionally qualified pre-doctoral, post-doctoral, and junior faculty researchers from the United States. The program is led by an experienced team of investigators from Brown University who collectively have several decades of experience conducting research among CJ-involved populations within local, national and international settings; and who have extensive mentoring experience with early career investigators. The mission of the CJRT program is to prepare scholars for independent NIH-funded clinical research careers focused on improving health outcomes related to substance use, HIV and HCV infection, and related co-morbidities among persons who are involved with the CJ system. The CJRT educational program is comprised of didactic education, mentored research, and experiential learning. CJRT scholars are enrolled for a two-year period and pursue research at their home institution under the guidance of both local and CJRT mentors. The program has the following three aims: 1) provide scholars with a solid foundation for clinical research related to CJ populations that includes skills in research methodology, scientific writing, grant writing, dissemination, and the ethics and practice of conducting research among vulnerable populations; 2) provide professional mentorship and guidance to support the career advancement of junior investigators; and 3) provide a mentored research experience including funds for pilot projects that provides a supportive pathway to research independence. For the next funding period, the CJRT program will highlight two new areas of training: 1) research related to the opioid crisis and overdose epidemic, given the public health urgency of this epidemic and direct relevance to CJ-populations; and 2) implementation science, given the need to effectively roll-out and expand access to evidence-based interventions for CJ-involved populations. Scientific guidance and program evaluation are strengthened by an Executive Committee and an External Advisory Committee.